1. Field of the Invention
The present invention relates to a control system for controlling an amount of charging or discharging of a battery for protecting batteries installed in hybrid vehicles.
2. Background Art
Conventionally, hybrid vehicles provided with a motor in addition to an engine are known. There are two types of hybrid vehicles: series hybrid vehicles and parallel hybrid vehicles. Series hybrid vehicles are driven by motors which are driven by the output of a generator driven by the engine.
Since the motor is not connected mechanically with the engine, the engine can be driven at an approximately constant rotation speed within a speed region wherein the engine can be driven at a lower fuel consumption rate and lower emission rate than the case of a conventional engine.
In contrast, in parallel hybrid vehicles, a motor directly connected to the engine assists the engine in rotating the drive shaft, and the motor is used as a generator for charging electric energy into a storage battery, and the electric energy generated by the motor is used for various electrical equipment in hybrid vehicles.
Thus, in parallel hybrid vehicles, since the driving load of the engine can be reduced, the fuel consumption and emission rates can be improved.
There are a few types of the above-described parallel hybrid vehicles, one is a type, in which a motor, connected directly to the output axis of the engine, functions as a generator for charging the battery when the hybrid vehicle decelerates, and the other one is a type in which both or either one of the engine or the motor can generate the driving force and a generator is additionally provided.
In such hybrid vehicles described above, the demands of the driver can be satisfied by preserving the electric energy of the battery (hereinafter, called xe2x80x9cstate of chargexe2x80x9d, that is the remaining battery charge), by carrying out a variety of controls such that the motor assists the engine at the time of acceleration, and the motor charges the battery by deceleration regeneration at the time deceleration.
However, the battery provided in a hybrid vehicle is used in such a way that the battery can supply an insufficient electric power, when the electric power to be supplied to the electric equipment provided in the vehicle exceeds the electric power generated by the motor. That is, a problem arises that when the engine is in an idling rotation mode, the electric power consumed by the electric equipment is liable to exceed the electric power generated by the motor, and thus the battery is liable to be over-discharged. Overdischarge is typically understood to occur when the state of charge of the battery is approximately 20%. If the battery installed in the hybrid vehicle is in the over-discharged state, the vehicle must be driven only by the engine, which results in causing degradation of the fuel consumption and the power performance of the hybrid vehicle.
It is, therefore, an object of the present invention to provide a control apparatus for hybrid vehicles for controlling charging and discharging rates for protecting the battery in response to the occurrence state of over-discharged state of the battery by detecting the over-discharge state.
The first aspect of the present invention provides a control device of a hybrid vehicles which comprises: an engine which outputs a propulsive force for the vehicle; a motor which is directly connected to said engine and which assists the output of the engine; a battery which supplies electric power to said motor and which is charged by electric energy generated by activating said motor as a generator when the assisting driving force is not necessary; an electric load whose electric energy is supplied by the electric power generated by the motor and the battery; and a battery protecting device which increases the rotation speed of said engine when an over-discharge state of said battery is detected and which stops supplying the electric power to said electric load when the over-discharge state further advances.
An effect of the control device of the hybrid vehicle according to the first aspect is that it provides the capability to protect the battery from falling into the over-discharge state by stepwise execution of the steps of xe2x80x9cincreasing the amount of generated power by increasing the engine idle speedxe2x80x9d and xe2x80x9ccutting the electric load by stopping the converter for supplying power to the electric equipmentxe2x80x9d, when the state of charge of the battery is decreasing while driving in the idle mode. In addition, the control device has a further effect that the control device of the present invention can prevent an increase in the fuel consumption and a reduction of the power of the hybrid vehicles.
A control device of a hybrid vehicle according to the second aspect, the hybrid vehicle having an engine which outputs propulsive force for the vehicle, a motor which is connected to said engine and which assists the output of the engine, a battery which supplies electric power to said motor and which is charged by electric energy generated by activating said motor as a generator when the assisting driving force is not necessary, an electric load whose electric energy is supplied by electric power generated by the motor and the battery, the control device comprises a contactor for connecting and disconnecting a current supply between said battery and said motor, an engine stopping device which stops said engine in response to predetermined driving conditions and a battery protecting device which restarts the engine when it is detected that the over-discharged state of the battery is further advanced after the engine is restarted.
The effect of the control device of the hybrid vehicle according to the second aspect is that it is capable of protecting the battery from falling into the over-discharge state by providing a contactor for connecting and disconnecting the current supply between the engine and the motor, an engine stop device for stopping the engine under certain driving conditions, and a battery protecting device which disconnects the contactor when the over-discharge state of the battery is detected for stopping the electric power supplyied to the electric equipment while the engine is in the idling mode. That is, when the battery falls into the over-discharge state and when it is possible to generate electricity by the motor, since the supply of the electric power to the other electric equipment can be completely stopped by disconnecting the contactor, all of the electric power generated by the motor can be directed to and stored in the battery, the advance of the over-discharge state can be prevented.